I'd like to punch whomever invented the Airdyne bike. It's so simple and looks so innocuous, yet it never fails to humble me and bring me to my knees. I've done 100 rep squats, drop-set leg presses, walking lunges until I fall over – you name it, I've tried it – and the quad pump I get from an all-out Airdyne bike sprint is more intense than any of those things.
Bike sprints aren't better than the aforementioned exercises for leg growth, but they definitely work the quads if you really put your all into it. Just look at sprint cyclists. Their quads are huge, even compared to regular cyclists. For the average lifter, bike sprints can augment your weight training and make for one hell of a pump at the end of your workout, which will assist in muscle growth.
There are endless ways to implement bike sprints. Some people like to do their sprints based on time, while others prefer to go by distance. Both are fine, but start with a distance that puts you in the 15-30 second range for each sprint, doing 3-4 intervals per workout and working up from there, either increasing the distance of the sprints, increasing the total intervals, or both.
Here's what the dreaded Tabata workout looks like: 8 rounds of 20 seconds on, 10 seconds off.
If you don't have an Airdyne bike or Assault Bike, a spin bike or regular exercise bike will suffice. Just keep the tension high enough that it feels challenging for the legs but low enough that you can still keep the RPMs reasonably high and it feels more like a sprint than a slow grind.